What exactly is a comet?
In the column last week we traced the orbit and speed of a famous comet on its long journey around the sun. This is interesting But when a comet, especially a big one, visits our skies, it is down right fascinating. It shines more brilliant than a star and it trail a stream of long golden hair. Sometimes it is bright enough to be seen by day and night for several weeks, and people all over the would gaze up at it in wonder.
The big telescopes are always watching for comets. They manage to spot five or six of them every year, but most of them are too small and too faint for our eyes to see. But maybe once in a lifetime our skies are visited by one of the big comets and nobody needs a telescope to see this razzle dazzle show. Its golden head shines brighter than the brightest star and its golden tail streams millions of miles over the sky.
The astronomers who keep watch on the skies see a comet coming towards the earth from afar. They know it isn't a meteor because of its foggy, hazy look. The round head of the comet seems to be a ball of golden gases. Inside the fuzzy ball is a small, brighter spot and the head of the comet looks somewhat like a star shining through a golden halo.
The bright center of a comet is called the nucleus, which is the same word we use for the core of the little atom. The golden halo around the nucleus is called the coma of the comet. The head of the comet is made of a bright nucleus in the center of a vast, hazy halo.
The long tail of the comet is made of finer than fine partcles. The tail is so filmy that there is hardly anything to it at all. We do not notice even when the earth passes right throw. it.
There is„ we think, less material in a comet’s tail than there is in the thin gases inside a light bulb, But the razzle dazzle light of a comet does not come from an electric switch.
A comet borrows its golden glory from the sun, the same blazing star which bathes our earth with daylight and sparkling sunshine The long, oval orbit of a comet takes it far, far out into space away from the sun. For most of the long trip, the comet is just a cluster of dark cold stones. It begins to glow only when its orbit brings it near the sun. The filmy tail grows and lights up as the comet swings in a loop to make a U turn close around the sun then back it goes around the rest of its long, dark, dreary orbit.
Comets are the bulkiest members of the sums family, Any lomet large enough to be seen is likely to be bigger than our globe yet on the scales, our world would weigh more than thousands of the biggest comets. The solid part of a comet may be a bundle of loose pebbles and perhaps frozen gases. At any rate, this nucleus is not solid enough to cut off the view of the distant sky, even when it passes directly in front of a star or a planet.